Forest fragmentation affects the biodiversity of birds

The results of this study were presented during FAPESP Week in North Carolina and published in Science.

By Samuel Antenor

Agência FAPESP – Deforestation processes are known worldwide as obstacles to the maintenance of forest ecosystems, and their distinct consequences for flora and fauna species could be worse for certain groups of animals. At least that’s what a new study led by Professor Mauro Galetti of the Ecology Department at the Rio Claro Campus of Universidade Estadual Paulista (Unesp) indicates.

According to the study, this is the case for birds, whose species diversity is threatened not only by deforestation of large green areas (e.g., for agroindustrial production) but also by the lack of continuous preservation of forests. These species are also threatened when there is a lack of conservation of sufficiently dense areas for their survival and reproduction.

Data that relate the reduction in forests to the survival of different tree species – and the reduction of trees as a factor contributing to a decline in the seed dispersion rate – are part of a broader research project exploring the manner in which fragmentation of the forests affects this biodiversity. These data were presented by Galetti on November 12 during FAPESP Week in Raleigh, North Carolina (U.S.).

The International Symposium – organized by FAPESP, the University of North Carolina at Chapel Hill, North Carolina State University (NCSU) and the Brazil Institute of the Woodrow Wilson International Center for Scholars (Washington D.C.) – brought together researchers from the two countries with the objective of intensifying and expanding studies conducted in São Paulo and North Carolina.

The research data, which were also published in Science, are part of the Thematic Project Effects of the defaunation gradient on plant herbivory, seed predation and dispersal: the Atlantic Rainforest perspective, which was funded by FAPESP and concluded in March at the Institute of Biosciences at Unesp Rio Claro.

Galetti and his team concentrated on investigating the behavior of several species of birds and their evolution capacity in environments that suffer from intense human actions, such as the remnants of the Atlantic Rainforest in southeast Brazil.

The Unesp professor also highlighted the reduction of a specific type of palm tree, the Euterpe edulis, as a result of direct human exploration, citing information found in the article published in Science. The study involved 15 researchers at 8 institutions in São Paulo, Paraná, Pará, Rio de Janeiro, Goiás, Mexico and Spain.

The palm tree described in Galetti’s lecture is a dominant species in the Atlantic Rainforest region, and its fruit are consumed by more than 58 species of birds. This palm tree, however, is also harvested for palm hearts, which puts it at risk due to human action.

In verifying the evolutionary consequences of this reduction in animal species, the study obtained data on the defaunation process that occurred in this biome, seeking to identify a loss or decline in the populations of medium- and large-scale native vertebrates.

Defaunation represents a significant threat not only for the Atlantic Rainforest but also for the biodiversity of several tropical ecosystems.

“We sought to verify how the loss of species at different levels affects biological systems with respect to physiology, vegetal reproducibility and animal behavior, including standards of migration, housing and diet health,” said Galetti.

Certain changes in these standards could lead to interruptions in ecosystem functioning, and, consequently, environmental degradation in the short or medium term. “In the long term, however, such changes could lead to alterations in the phenotypes and genetic structures of animal populations,” he said.

For Galetti, the data from this study indicate that the researchers must identify needs and detail possible prognoses to ensure adequate time for adaptation to the conditions characterized by a possible decline in species.

Composed largely of herbivorous and frugivorous species, medium- and large-scale fauna include animals that are important for seed dispersal, which helps to control plant growth through herbivory and predation of seeds.

According to Galetti, illegal hunting has considerably reduced several of these animal species in distinct tropical areas, especially in the Atlantic Rainforest, which could have profound effects on the diversity and the composition of vegetal species.

With only 12% of the forest remaining, the Atlantic Rainforest still contains 8% of the world’s bird species and has high endemism rates.

Related species

Large migrations among bird populations suggest that Euterpe edulis shares a common evolutionary history with these birds, which are important agents for germination of this palm tree species.

“Its seeds are spread through regurgitation or defecation. Still, there is evidence of a reduction in bird species with the capacity to collect large seeds, such as toucans, which makes vulnerability to seed dispersion even greater among E. edulis palm trees,” Galetti notes.

According to the researcher, differences in seed sizes occur because of the growing isolation of increasingly fragmented forests.

The size of the seed is related to loss of water and germination. The larger the seed, the lower the exposed surface area in proportion to volume. This phenomenon worsens the problem, given that the seeds do not germinate with less than 20% of their surface exposed to water.

“Defaunation creates a new selection regime for the evolution of plants in the Anthropocene. These changes could go unnoticed, but are capable of leading to the extinction of several species in future climatic scenarios,” said Galetti.

The study was presented at the panel on biodiversity, which had presentations from researchers Maritta Koch-Weser, of the Institute of Advanced Studies at Universidade de São Paulo (USP), Erin Sills, of North Carolina State University, and Daniel Janies, of the University of North Carolina-Charlotte.

Brazilian nature

FAPESP Week in North Carolina also included an exhibition of Brazilian Nature – Mystery and Destiny in two separate locations.

The first show opened at the James B. Hunter Library in the Institute of Emerging Issues at NCSU in Raleigh, where it was on exhibit through November 20. The second show opened on November 13 in the Student Union at University of North Carolina-Charlotte.

With 37 panels, the exhibition covers the work of German naturalist Carl Friedrich Philipp von Martius (1794-1868) and allows visitors to compare original images produced in the 19th century with current photographs and plants.Some of the photographs were produced during research conducted under the auspices of the Phanerogamic Flora of São Paulo State and the Research Program on the Characterization, Conservation, Recovery and Sustainable Use of Biodiversity (BIOTA-FAPESP).

The digitalized panels from the exhibition can be viewed with captions in Portuguese, English, Spanish, Japanese and German at the following website: www.fapesp.br/publicacoes/braziliannature.